ffmpeg−utils − FFmpeg utilities
This document describes some generic features and utilities provided by the libavutil library.
This section documents the syntax and formats employed by the FFmpeg libraries and tools.
FFmpeg adopts the following quoting and escaping mechanism, unless explicitly specified. The following rules are applied:
• |
’ and \ are special characters (respectively used for quoting and escaping). In addition to them, there might be other special characters depending on the specific syntax where the escaping and quoting are employed. | ||
• |
A special character is escaped by prefixing it with a \. | ||
• |
All characters enclosed between ’’ are included literally in the parsed string. The quote character ’ itself cannot be quoted, so you may need to close the quote and escape it. | ||
• |
Leading and trailing whitespaces, unless escaped or quoted, are removed from the parsed string. |
Note that you may need to add a second level of escaping when using the command line or a script, which depends on the syntax of the adopted shell language.
The function "av_get_token" defined in libavutil/avstring.h can be used to parse a token quoted or escaped according to the rules defined above.
The tool tools/ffescape in the FFmpeg source tree can be used to automatically quote or escape a string in a script.
Examples
• |
Escape the string "Crime d'Amour" containing the "'" special character: |
Crime d\'Amour
• |
The string above contains a quote, so the "'" needs to be escaped when quoting it: |
'Crime d'\''Amour'
• |
Include leading or trailing whitespaces using quoting: |
' this string starts and ends with whitespaces '
• |
Escaping and quoting can be mixed together: |
' The string '\'string\'' is a string '
• |
To include a literal \ you can use either escaping or quoting: |
'c:\foo' can be written as c:\\foo
The accepted syntax is:
[(YYYY−MM−DD|YYYYMMDD)[T|t|
]]((HH:MM:SS[.m...]]])|(HHMMSS[.m...]]]))[Z]
now
If the value is "now" it takes the current time.
Time is local time unless Z is appended, in which case it is interpreted as UTC. If the year-month-day part is not specified it takes the current year-month-day.
There are two accepted syntaxes for expressing time duration.
[−][<HH>:]<MM>:<SS>[.<m>...]
HH expresses the number of hours, MM the number of minutes for a maximum of 2 digits, and SS the number of seconds for a maximum of 2 digits. The m at the end expresses decimal value for SS.
or
[−]<S>+[.<m>...][s|ms|us]
S expresses the number of seconds, with the optional decimal part m. The optional literal suffixes s, ms or us indicate to interpret the value as seconds, milliseconds or microseconds, respectively.
In both expressions, the optional − indicates negative duration.
Examples
The following examples are all valid time duration:
55 |
55 seconds |
|||
0.2 |
0.2 seconds |
200ms
200 milliseconds, that’s 0.2s
200000us
200000 microseconds, that’s 0.2s
12:03:45
12 hours, 03 minutes and 45 seconds
23.189
23.189 seconds
Specify the size of the sourced video, it may be a string of the form widthxheight, or the name of a size abbreviation.
The following
abbreviations are recognized:
ntsc
720x480
pal |
720x576 |
qntsc
352x240
qpal
352x288
sntsc
640x480
spal
768x576
film
352x240
ntsc-film
352x240
sqcif
128x96
qcif
176x144
cif |
352x288 |
4cif
704x576
16cif
1408x1152
qqvga
160x120
qvga
320x240
vga |
640x480 |
svga
800x600
xga |
1024x768 |
uxga
1600x1200
qxga
2048x1536
sxga
1280x1024
qsxga
2560x2048
hsxga
5120x4096
wvga
852x480
wxga
1366x768
wsxga
1600x1024
wuxga
1920x1200
woxga
2560x1600
wqsxga
3200x2048
wquxga
3840x2400
whsxga
6400x4096
whuxga
7680x4800
cga |
320x200 |
|||
ega |
640x350 |
hd480
852x480
hd720
1280x720
hd1080
1920x1080
2k |
2048x1080 |
2kflat
1998x1080
2kscope
2048x858
4k |
4096x2160 |
4kflat
3996x2160
4kscope
4096x1716
nhd |
640x360 |
hqvga
240x160
wqvga
400x240
fwqvga
432x240
hvga
480x320
qhd |
960x540 |
2kdci
2048x1080
4kdci
4096x2160
uhd2160
3840x2160
uhd4320
7680x4320
Specify the frame rate of a video, expressed as the number of frames generated per second. It has to be a string in the format frame_rate_num/frame_rate_den, an integer number, a float number or a valid video frame rate abbreviation.
The following
abbreviations are recognized:
ntsc
30000/1001
pal |
25/1 |
qntsc
30000/1001
qpal
25/1
sntsc
30000/1001
spal
25/1
film
24/1
ntsc-film
24000/1001
A ratio can be expressed as an expression, or in the form numerator:denominator.
Note that a ratio with infinite (1/0) or negative value is considered valid, so you should check on the returned value if you want to exclude those values.
The undefined value can be expressed using the "0:0" string.
It can be the name of a color as defined below (case insensitive match) or a "[0x|#]RRGGBB[AA]" sequence, possibly followed by @ and a string representing the alpha component.
The alpha component may be a string composed by "0x" followed by an hexadecimal number or a decimal number between 0.0 and 1.0, which represents the opacity value (0x00 or 0.0 means completely transparent, 0xff or 1.0 completely opaque). If the alpha component is not specified then 0xff is assumed.
The string random will result in a random color.
The following
names of colors are recognized:
AliceBlue
0xF0F8FF
AntiqueWhite
0xFAEBD7
Aqua
0x00FFFF
Aquamarine
0x7FFFD4
Azure
0xF0FFFF
Beige
0xF5F5DC
Bisque
0xFFE4C4
Black
0x000000
BlanchedAlmond
0xFFEBCD
Blue
0x0000FF
BlueViolet
0x8A2BE2
Brown
0xA52A2A
BurlyWood
0xDEB887
CadetBlue
0x5F9EA0
Chartreuse
0x7FFF00
Chocolate
0xD2691E
Coral
0xFF7F50
CornflowerBlue
0x6495ED
Cornsilk
0xFFF8DC
Crimson
0xDC143C
Cyan
0x00FFFF
DarkBlue
0x00008B
DarkCyan
0x008B8B
DarkGoldenRod
0xB8860B
DarkGray
0xA9A9A9
DarkGreen
0x006400
DarkKhaki
0xBDB76B
DarkMagenta
0x8B008B
DarkOliveGreen
0x556B2F
Darkorange
0xFF8C00
DarkOrchid
0x9932CC
DarkRed
0x8B0000
DarkSalmon
0xE9967A
DarkSeaGreen
0x8FBC8F
DarkSlateBlue
0x483D8B
DarkSlateGray
0x2F4F4F
DarkTurquoise
0x00CED1
DarkViolet
0x9400D3
DeepPink
0xFF1493
DeepSkyBlue
0x00BFFF
DimGray
0x696969
DodgerBlue
0x1E90FF
FireBrick
0xB22222
FloralWhite
0xFFFAF0
ForestGreen
0x228B22
Fuchsia
0xFF00FF
Gainsboro
0xDCDCDC
GhostWhite
0xF8F8FF
Gold
0xFFD700
GoldenRod
0xDAA520
Gray
0x808080
Green
0x008000
GreenYellow
0xADFF2F
HoneyDew
0xF0FFF0
HotPink
0xFF69B4
IndianRed
0xCD5C5C
Indigo
0x4B0082
Ivory
0xFFFFF0
Khaki
0xF0E68C
Lavender
0xE6E6FA
LavenderBlush
0xFFF0F5
LawnGreen
0x7CFC00
LemonChiffon
0xFFFACD
LightBlue
0xADD8E6
LightCoral
0xF08080
LightCyan
0xE0FFFF
LightGoldenRodYellow
0xFAFAD2
LightGreen
0x90EE90
LightGrey
0xD3D3D3
LightPink
0xFFB6C1
LightSalmon
0xFFA07A
LightSeaGreen
0x20B2AA
LightSkyBlue
0x87CEFA
LightSlateGray
0x778899
LightSteelBlue
0xB0C4DE
LightYellow
0xFFFFE0
Lime
0x00FF00
LimeGreen
0x32CD32
Linen
0xFAF0E6
Magenta
0xFF00FF
Maroon
0x800000
MediumAquaMarine
0x66CDAA
MediumBlue
0x0000CD
MediumOrchid
0xBA55D3
MediumPurple
0x9370D8
MediumSeaGreen
0x3CB371
MediumSlateBlue
0x7B68EE
MediumSpringGreen
0x00FA9A
MediumTurquoise
0x48D1CC
MediumVioletRed
0xC71585
MidnightBlue
0x191970
MintCream
0xF5FFFA
MistyRose
0xFFE4E1
Moccasin
0xFFE4B5
NavajoWhite
0xFFDEAD
Navy
0x000080
OldLace
0xFDF5E6
Olive
0x808000
OliveDrab
0x6B8E23
Orange
0xFFA500
OrangeRed
0xFF4500
Orchid
0xDA70D6
PaleGoldenRod
0xEEE8AA
PaleGreen
0x98FB98
PaleTurquoise
0xAFEEEE
PaleVioletRed
0xD87093
PapayaWhip
0xFFEFD5
PeachPuff
0xFFDAB9
Peru
0xCD853F
Pink
0xFFC0CB
Plum
0xDDA0DD
PowderBlue
0xB0E0E6
Purple
0x800080
Red |
0xFF0000 |
RosyBrown
0xBC8F8F
RoyalBlue
0x4169E1
SaddleBrown
0x8B4513
Salmon
0xFA8072
SandyBrown
0xF4A460
SeaGreen
0x2E8B57
SeaShell
0xFFF5EE
Sienna
0xA0522D
Silver
0xC0C0C0
SkyBlue
0x87CEEB
SlateBlue
0x6A5ACD
SlateGray
0x708090
Snow
0xFFFAFA
SpringGreen
0x00FF7F
SteelBlue
0x4682B4
Tan |
0xD2B48C |
Teal
0x008080
Thistle
0xD8BFD8
Tomato
0xFF6347
Turquoise
0x40E0D0
Violet
0xEE82EE
Wheat
0xF5DEB3
White
0xFFFFFF
WhiteSmoke
0xF5F5F5
Yellow
0xFFFF00
YellowGreen
0x9ACD32
A channel layout specifies the spatial disposition of the channels in a multi-channel audio stream. To specify a channel layout, FFmpeg makes use of a special syntax.
Individual channels are identified by an id, as given by the table below:
FL |
front left |
|||
FR |
front right |
|||
FC |
front center |
|||
LFE |
low frequency |
|||
BL |
back left |
|||
BR |
back right |
|||
FLC |
front left-of-center |
|||
FRC |
front right-of-center |
|||
BC |
back center |
|||
SL |
side left |
|||
SR |
side right |
|||
TC |
top center |
|||
TFL |
top front left |
|||
TFC |
top front center |
|||
TFR |
top front right |
|||
TBL |
top back left |
|||
TBC |
top back center |
|||
TBR |
top back right |
|||
DL |
downmix left |
|||
DR |
downmix right |
|||
WL |
wide left |
|||
WR |
wide right |
|||
SDL |
surround direct left |
|||
SDR |
surround direct right |
LFE2
low frequency 2
Standard channel
layout compositions can be specified by using the following
identifiers:
mono
FC
stereo
FL+FR
2.1 |
FL+FR+LFE |
|||
3.0 |
FL+FR+FC |
3.0(back)
FL+FR+BC
4.0 |
FL+FR+FC+BC |
quad
FL+FR+BL+BR
quad(side)
FL+FR+SL+SR
3.1 |
FL+FR+FC+LFE |
|||
5.0 |
FL+FR+FC+BL+BR |
5.0(side)
FL+FR+FC+SL+SR
4.1 |
FL+FR+FC+LFE+BC |
|||
5.1 |
FL+FR+FC+LFE+BL+BR |
5.1(side)
FL+FR+FC+LFE+SL+SR
6.0 |
FL+FR+FC+BC+SL+SR |
6.0(front)
FL+FR+FLC+FRC+SL+SR
3.1.2
FL+FR+FC+LFE+TFL+TFR
hexagonal
FL+FR+FC+BL+BR+BC
6.1 |
FL+FR+FC+LFE+BC+SL+SR |
|||
6.1 |
FL+FR+FC+LFE+BL+BR+BC |
6.1(front)
FL+FR+LFE+FLC+FRC+SL+SR
7.0 |
FL+FR+FC+BL+BR+SL+SR |
7.0(front)
FL+FR+FC+FLC+FRC+SL+SR
7.1 |
FL+FR+FC+LFE+BL+BR+SL+SR |
7.1(wide)
FL+FR+FC+LFE+BL+BR+FLC+FRC
7.1(wide−side)
FL+FR+FC+LFE+FLC+FRC+SL+SR
5.1.2
FL+FR+FC+LFE+BL+BR+TFL+TFR
octagonal
FL+FR+FC+BL+BR+BC+SL+SR
cube
FL+FR+BL+BR+TFL+TFR+TBL+TBR
5.1.4
FL+FR+FC+LFE+BL+BR+TFL+TFR+TBL+TBR
7.1.2
FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR
7.1.4
FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR+TBL+TBR
hexadecagonal
FL+FR+FC+BL+BR+BC+SL+SR+WL+WR+TBL+TBR+TBC+TFC+TFL+TFR
downmix
DL+DR
22.2
FL+FR+FC+LFE+BL+BR+FLC+FRC+BC+SL+SR+TC+TFL+TFC+TFR+TBL+TBC+TBR+LFE2+TSL+TSR+BFC+BFL+BFR
A custom channel layout can be specified as a sequence of terms, separated by ’+’. Each term can be:
• |
the name of a single channel (e.g. FL, FR, FC, LFE, etc.), each optionally containing a custom name after a ’@’, (e.g. FL@Left, FR@Right, FC@Center, LFE@Low_Frequency, etc.) |
A standard channel layout can be specified by the following:
• |
the name of a single channel (e.g. FL, FR, FC, LFE, etc.) | ||
• |
the name of a standard channel layout (e.g. mono, stereo, 4.0, quad, 5.0, etc.) | ||
• |
a number of channels, in decimal, followed by ’c’, yielding the default channel layout for that number of channels (see the function "av_channel_layout_default"). Note that not all channel counts have a default layout. | ||
• |
a number of channels, in decimal, followed by ’C’, yielding an unknown channel layout with the specified number of channels. Note that not all channel layout specification strings support unknown channel layouts. | ||
• |
a channel layout mask, in hexadecimal starting with "0x" (see the "AV_CH_*" macros in libavutil/channel_layout.h. |
Before libavutil version 53 the trailing character "c" to specify a number of channels was optional, but now it is required, while a channel layout mask can also be specified as a decimal number (if and only if not followed by "c" or "C").
See also the function "av_channel_layout_from_string" defined in libavutil/channel_layout.h.
When evaluating an arithmetic expression, FFmpeg uses an internal formula evaluator, implemented through the libavutil/eval.h interface.
An expression may contain unary, binary operators, constants, and functions.
Two expressions expr1 and expr2 can be combined to form another expression "expr1;expr2". expr1 and expr2 are evaluated in turn, and the new expression evaluates to the value of expr2.
The following binary operators are available: "+", "−", "*", "/", "ˆ".
The following unary operators are available: "+", "−".
The following
functions are available:
abs(x)
Compute absolute value of x.
acos(x)
Compute arccosine of x.
asin(x)
Compute arcsine of x.
atan(x)
Compute arctangent of x.
atan2(x, y)
Compute principal value of the arc tangent of y/x.
between(x, min, max)
Return 1 if x is greater than or equal to min and lesser than or equal to max, 0 otherwise.
bitand(x, y)
bitor(x, y)
Compute bitwise and/or operation on x and y.
The results of the evaluation of x and y are converted to integers before executing the bitwise operation.
Note that both the conversion to integer and the conversion back to floating point can lose precision. Beware of unexpected results for large numbers (usually 2ˆ53 and larger).
ceil(expr)
Round the value of expression expr upwards to the nearest integer. For example, "ceil(1.5)" is "2.0".
clip(x, min, max)
Return the value of x clipped between min and max.
cos(x)
Compute cosine of x.
cosh(x)
Compute hyperbolic cosine of x.
eq(x, y)
Return 1 if x and y are equivalent, 0 otherwise.
exp(x)
Compute exponential of x (with base "e", the Euler’s number).
floor(expr)
Round the value of expression expr downwards to the nearest integer. For example, "floor(−1.5)" is "−2.0".
gauss(x)
Compute Gauss function of x, corresponding to "exp(−x*x/2) / sqrt(2*PI)".
gcd(x, y)
Return the greatest common divisor of x and y. If both x and y are 0 or either or both are less than zero then behavior is undefined.
gt(x, y)
Return 1 if x is greater than y, 0 otherwise.
gte(x, y)
Return 1 if x is greater than or equal to y, 0 otherwise.
hypot(x, y)
This function is similar to the C function with the same name; it returns "sqrt(x*x + y*y)", the length of the hypotenuse of a right triangle with sides of length x and y, or the distance of the point (x, y) from the origin.
if(x, y)
Evaluate x, and if the result is non-zero return the result of the evaluation of y, return 0 otherwise.
if(x, y, z)
Evaluate x, and if the result is non-zero return the evaluation result of y, otherwise the evaluation result of z.
ifnot(x, y)
Evaluate x, and if the result is zero return the result of the evaluation of y, return 0 otherwise.
ifnot(x, y, z)
Evaluate x, and if the result is zero return the evaluation result of y, otherwise the evaluation result of z.
isinf(x)
Return 1.0 if x is +/−INFINITY, 0.0 otherwise.
isnan(x)
Return 1.0 if x is NAN, 0.0 otherwise.
ld(var)
Load the value of the internal variable with number var, which was previously stored with st(var, expr). The function returns the loaded value.
lerp(x, y, z)
Return linear interpolation between x and y by amount of z.
log(x)
Compute natural logarithm of x.
lt(x, y)
Return 1 if x is lesser than y, 0 otherwise.
lte(x, y)
Return 1 if x is lesser than or equal to y, 0 otherwise.
max(x, y)
Return the maximum between x and y.
min(x, y)
Return the minimum between x and y.
mod(x, y)
Compute the remainder of division of x by y.
not(expr)
Return 1.0 if expr is zero, 0.0 otherwise.
pow(x, y)
Compute the power of x elevated y, it is equivalent to "(x)ˆ(y)".
print(t)
print(t, l)
Print the value of expression t with loglevel l. If l is not specified then a default log level is used. Returns the value of the expression printed.
Prints t with loglevel l
random(x)
Return a pseudo random value between 0.0 and 1.0. x is the index of the internal variable which will be used to save the seed/state.
root(expr, max)
Find an input value for which the function represented by expr with argument ld(0) is 0 in the interval 0..max.
The expression in expr must denote a continuous function or the result is undefined.
ld(0) is used to represent the function input value, which means that the given expression will be evaluated multiple times with various input values that the expression can access through ld(0). When the expression evaluates to 0 then the corresponding input value will be returned.
round(expr)
Round the value of expression expr to the nearest integer. For example, "round(1.5)" is "2.0".
sgn(x)
Compute sign of x.
sin(x)
Compute sine of x.
sinh(x)
Compute hyperbolic sine of x.
sqrt(expr)
Compute the square root of expr. This is equivalent to "(expr)ˆ.5".
squish(x)
Compute expression "1/(1 + exp(4*x))".
st(var, expr)
Store the value of the expression expr in an internal variable. var specifies the number of the variable where to store the value, and it is a value ranging from 0 to 9. The function returns the value stored in the internal variable. Note, Variables are currently not shared between expressions.
tan(x)
Compute tangent of x.
tanh(x)
Compute hyperbolic tangent of x.
taylor(expr, x)
taylor(expr, x, id)
Evaluate a Taylor series at x, given an expression representing the ld(id)−th derivative of a function at 0.
When the series does not converge the result is undefined.
ld(id) is used to represent the derivative order in expr, which means that the given expression will be evaluated multiple times with various input values that the expression can access through ld(id). If id is not specified then 0 is assumed.
Note, when you have the derivatives at y instead of 0, "taylor(expr, x−y)" can be used.
time(0)
Return the current (wallclock) time in seconds.
trunc(expr)
Round the value of expression expr towards zero to the nearest integer. For example, "trunc(−1.5)" is "−1.0".
while(cond, expr)
Evaluate expression expr while the expression cond is non-zero, and returns the value of the last expr evaluation, or NAN if cond was always false.
The following constants are available:
PI |
area of the unit disc, approximately 3.14 |
|||
E |
exp(1) (Euler’s number), approximately 2.718 |
|||
PHI |
golden ratio (1+sqrt(5))/2, approximately 1.618 |
Assuming that an expression is considered "true" if it has a non-zero value, note that:
"*" works like AND
"+" works like OR
For example the construct:
if (A AND B) then C
is equivalent to:
if(A*B, C)
In your C code, you can extend the list of unary and binary functions, and define recognized constants, so that they are available for your expressions.
The evaluator also recognizes the International System unit prefixes. If ’i’ is appended after the prefix, binary prefixes are used, which are based on powers of 1024 instead of powers of 1000. The ’B’ postfix multiplies the value by 8, and can be appended after a unit prefix or used alone. This allows using for example ’KB’, ’MiB’, ’G’ and ’B’ as number postfix.
The list of available International System prefixes follows, with indication of the corresponding powers of 10 and of 2.
y |
10ˆ−24 / 2ˆ−80 |
|||
z |
10ˆ−21 / 2ˆ−70 |
|||
a |
10ˆ−18 / 2ˆ−60 |
|||
f |
10ˆ−15 / 2ˆ−50 |
|||
p |
10ˆ−12 / 2ˆ−40 |
|||
n |
10ˆ−9 / 2ˆ−30 |
|||
u |
10ˆ−6 / 2ˆ−20 |
|||
m |
10ˆ−3 / 2ˆ−10 |
|||
c |
10ˆ−2 |
|||
d |
10ˆ−1 |
|||
h |
10ˆ2 |
|||
k |
10ˆ3 / 2ˆ10 |
|||
K |
10ˆ3 / 2ˆ10 |
|||
M |
10ˆ6 / 2ˆ20 |
|||
G |
10ˆ9 / 2ˆ30 |
|||
T |
10ˆ12 / 2ˆ40 |
|||
P |
10ˆ15 / 2ˆ50 |
|||
E |
10ˆ18 / 2ˆ60 |
|||
Z |
10ˆ21 / 2ˆ70 |
|||
Y |
10ˆ24 / 2ˆ80 |
ffmpeg(1), ffplay(1), ffprobe(1), libavutil(3)
The FFmpeg developers.
For details about the authorship, see the Git history of the project (https://git.ffmpeg.org/ffmpeg), e.g. by typing the command git log in the FFmpeg source directory, or browsing the online repository at <https://git.ffmpeg.org/ffmpeg>.
Maintainers for the specific components are listed in the file MAINTAINERS in the source code tree.